I have FreeBSD 9.0-RC3 installed on an HP Thin Client that has a Mobile AMD Sempron(tm) Processor 2100+. I am trying to get cpufreq and powerd to manage the frequency of the processor, but I'm not having any luck. Here's some lines from dmesg:

This isn't surprising - small-form-factor boxes (like the T5730w; is that what you have?) are often built to run cool and low-power anyway. The Sempron 2100+ is 9W and built to be fanless, which fits that model.

If you're actually having heat issues, you might be able to replace a chassis fan or otherwise improve air flow, but I think the CPU's not going to cooperate.